The objective of the research is to examine the role of response error (trait desirability, need for social approval, response acquiescence) in field studies of the prevalence of psychiatric impairment. Data will be acquired by household interview using a stratified sample with optimal allocation by sex, socioeconomic status, and ethnicity. The sampling frame to be used is the almost 8,000 respondents interviewed in 1974 in Alameda County by the Human Population Laboratory for Epidemiologic Studies. Ethnicity is defined using ethnic heritage (e.g., Blacks, Mexican Americans, Amerindians) and religion (e.g., Jews, Mormons, Fundamentalist Protestants). Response tendencies will be studied in relation to four brief psychiatric screening instruments: the Health Opinion Survey, the Affect-Balance Scale, the Self-Rating Depression Scale, and the Psychiatric Epidemiology Research Interview. Data analysis will focus on the magnitude and direction of error introduced by response tendencies in contrasting sex, socioeconomic status, and ethnic groups. For example, how much variance in symptom scores are attributable to response tendencies as compared to sex, socioeconomic status, and ethnicity.